Piezoresistor height sensing cantilever

ABSTRACT

A device comprising at least one cantilever comprising at least one piezoresistor is described, where the cantilevers comprise silicon nitride or silicon carbide and the piezoresistors comprise doped silicon. Methods for making and using such a device are also provided.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Applications No.61/052,864, filed May 13, 2008, and U.S. Provisional Application No.61/167,853, filed Apr. 8, 2009, each of which are incorporated byreference in their entirety.

FEDERAL FUNDING

The claimed inventions described herein were developed with use of NIHSBIR funds grant no. 2 R33 HG002978-02. The government has certainrights in the invention.

BACKGROUND

Silicon has been used frequently for the manufacture of cantileversadapted for instrumentations such as scanning probe and atomic forcemicroscope. A cantilever can not only act as an arm providing a tip atits proximate end for applications, such as lithography and surfacetopography scanning, but can also provide a sensing mechanism to detectthe distance between the substrate surface and the cantilever itself.See, for example, M. Tortonese et al., Appl. Phys. Lett. 62 (1993), pp.834-836; U.S. Pat. No. 5,595,942 to T. Albrecht et al. More recently,piezoresistors have been incorporated into such silicon-based device.See, for example, R. Jumpertz, et al., In Proceedings, EuropeanSolid-State Device Research Conference (ESSDRC), pp. 680-683 (1997); F.Goericke et al., Sensors and Actuators A143 (2008), pp. 181-190; A.Gaitas, “Novel single cell disease markers with a hybrid AFM scanningpiezo-thermal probe.” NIH grant 1R43GM084520-01, 15 May 2008.

One significant drawback of using silicon as a base material for thecantilever is the electrical charging of the probe and cantilever, and alack of control of the electrostatic fields in the device, becausesilicon is an electrical conductor. Particularly, when the applicationsinvolve biological materials, either to sense these materials or todeposit these materials onto a substrate using lithography, the presenceof an uncontrolled electrical field and other electrical chargingmechanisms can adversely impact the applications.

Additionally, the commonly available piezoresistor utilizeslightly-doped silicon or intrinsic silicon often to maximize the piezoresponse. However, it is also generally known in the art that while thelightly-doped silicon design can provide a large piezo response, it cansuffer a drawback of needing for temperature compensation, which isoften difficult. See, for example, Y. Kanda, “IEEE Trans. Elec. Dev.ED-29, pp. 64-70 (1982).

Thus, there exists a need to provide a better height-sensing mechanismfor the design of the cantilever.

SUMMARY

Provided herein are devices, apparatuses, compositions, methods ofmaking same, and methods of using same.

One embodiment provides a device comprising at least one cantilevercomprising at least one piezoresistor, where the at least onecantilevers comprise silicon nitride or silicon carbide, the at leastone piezoresistor is disposed on the at least one cantilever, and the atleast one piezoresistor comprises silicon and at least one dopant.

Another embodiment provides a method comprising forming at least onepiezoresistor in a handle wafer, forming at least one cantileverdisposed on the handle wafer, annealing the handle wafer for a timesufficient to allow the at least one piezoresistor to contact the atleast one cantilever, and separating the combined at least onepiezoresistor and the at least one cantilever from at least a portion ofthe remaining handle wafer.

Yet another embodiment provides a method comprising measuring at leastone resistance of at least one piezoresistor, determining a maximum orminimum resistance from those measurements, determining a specificlocation corresponding to the location of the maximum or minimumresistance, and calculating a tip deflection.

Still another embodiment provides a method comprising measuring at leastone resistance of at least one strain gauge. determining a maximum orminimum resistance from those measurements, determining a specificlocation corresponding to the location of the maximum or minimumresistance, and calculating a tip deflection.

At least one advantage of at least one embodiment includes improvedcontrol over electrostatic fields.

At least one advantage of at least one embodiment includes decreasedelectrical noise in measured signals.

At least one advantage of at least one embodiment includes improvedcompatibility with biological materials.

At least one advantage of at least one embodiment includes enhancedresilience to changes in temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the depth wise concentration profile of boron in the handlewafer in one embodiment.

FIGS. 2A-2J show optical images of various cantilevers withpiezoresistor designs: 2A: cantilevers with ‘twist’ sensors; 2B close-upof “twist” sensors on cantilever end; 2C: close-up of reference ‘twist’sensors; 2D: view of general pad and die design; 2E: Long longitudinalsensors, contacts off-cantilever; 2F: short longitudinal sensors,contacts on-cantilever; 2G: longitudinal sensors, contactsoff-cantilever; 2H: integrated longitudinal sensors, contactsoff-cantilever, with thermal active pen heater wires; 2I: ‘twist’sensors, prior to handle bonding; 2J: close-up, long longitudinalsensors, on-cantilever contact, prior to handle bonding.

FIGS. 3A-3I provides schematics of a process flowchart of a fabricationprocedure in one embodiment.

DETAILED DESCRIPTION

All references cited herein are incorporated by reference in theirentirety.

Introduction

For practice of the various embodiments described herein, lithography,microlithography, and nanolithography instruments, pen arrays, activepens, passive pens, inks, patterning compounds, kits, ink delivery,software, and accessories for direct-write printing and patterning canbe obtained from NanoInk, Inc., Chicago, Ill. Instrumentation includesthe NSCRIPTOR. Software includes INKCAD software (NanoInk, Chicago,Ill.), providing user interface for lithography design and control.E-Chamber can be used for environmental control. Dip PenNanolithography™ and DPN™ are trademarks of NanoInk, Inc.

The following patents and co-pending applications related todirect-write printing with use of cantilevers, tips, and patterningcompounds are hereby incorporated by reference in their entirety and canbe used in the practice of the various embodiments described herein,including inks, patterning compounds, software, ink delivery devices,and the like:

U.S. Pat. No. 6,635,311 to Mirkin et al., which describes fundamentalaspects of DPN printing including inks, tips, substrates, and otherinstrumentation parameters and patterning methods;

U.S. Pat. No. 6,827,979 to Mirkin et al., which further describesfundamental aspects of DPN printing including software control, etchingprocedures, nanoplotters, and complex and combinatorial array formation.

U.S. patent publication number 2002/0122873 A1 published Sep. 5, 2002(“Nanolithography Methods and Products Produced Therefor and ProducedThereby”), which describes aperture embodiments and driving forceembodiments of DPN printing.

U.S. Pat. No. 7,279,046 to Eby et al. (“Methods and Apparatus forAligning Patterns on a Substrate”), which describes alignment methodsfor DPN printing.

U.S. Pat. No. 7,060,977 to Dupeyrat et al. (“NanolithographicCalibration Methods”), which describes calibration methods for DPNprinting.

U.S. Patent Publication 2003/0068446, published Apr. 10, 2003 to Mirkinet al. (“Protein and Peptide Nanoarrays”), which describes nanoarrays ofproteins and peptides.

U.S. Pat. No. 7,361,310 to Mirkin et al. (“Direct-Write NanolithographicDeposition of Nucleic Acids from Nanoscopic Tips”), which describesnucleic acid.

U.S. Pat. No. 7,273,636 to Mirkin et al. (“Patterning of Solid StateFeatures by Direct-Write Nanolithographic Printing”), which describesreactive patterning and sol gel inks (now published Aug. 28, 2003 as2003/0162004).

U.S. Pat. Nos. 6,642,129 and 6,867,443 to Liu et al. (“Parallel,Individually Addressable Probes for Nanolithography”), describing activepen arrays.

U.S. Patent Publication 2003/0007242, published Jan. 9, 2003 to Schwartz(“Enhanced Scanning Probe Microscope and Nanolithographic Methods UsingSame”).

U.S. Patent Publication 2003/0005755, published Jan. 9, 2003 to Schwartz(“Enhanced Scanning Probe Microscope”).

U.S. Pat. No. 7,093,056 to Demers et al., describing catalystnanostructures and carbon nanotube applications.

U.S. Pat. No. 7,199,305 to Cruchon-Dupeyrat et al., and U.S. Pat. No.7,102,656 to Mirkin et al., describing printing of proteins andconducting polymers respectively.

U.S. Pat. No. 7,005,378 to Crocker et al., describing conductivematerials as patterning compounds.

U.S. patent application Ser. No. 10/689,547 filed Oct. 21, 2003, nowpublished as 2004/0175631 on Sep. 9, 2004, describing mask applicationsincluding photomask repair.

U.S. Pat. No. 7,034,854 Cruchon-Dupeyrat et al., describingmicrofluidics and ink delivery.

U.S. patent application Ser. No. 10/788,414 filed Mar. 1, 2004, nowpublished as 2005/0009206 on Jan. 13, 2005 describing printing ofpeptides and proteins.

U.S. Pat. No. 7,326,380 to Mirkin et al., describing ROMP methods andcombinatorial arrays.

U.S. Pat. No. 7,491,422 to Zhang et al., describing stamp tip or polymercoated tip applications.

U.S. patent application Ser. No. 11/065,694 filed Feb. 25, 2005, nowpublished as 2005/0235869 on Oct. 27, 2005, describing tiplesscantilevers and flat panel display applications.

US Patent publication 2006/001,4001 published Jan. 19, 2006 describingetching of nanostructures made by DPN methods.

WO 2004/105046 to Liu & Mirkin published Dec. 2, 2004 describes scanningprobes for contact printing.

U.S. patent application Ser. No. “Active Pen Nanolithography,”11/268,740 to Shile et al. filed Nov. 8, 2005 describes for examplethermocompression bonding and silicon handle wafers.

DPN methods are also described in Ginger et al., “The Evolution ofDip-Pen Nanolithography,” Angew. Chem. Int. Ed. 2004, 43, 30-45,including description of high-throughput parallel methods. See alsoSalaita et al., “Applications of Dip-Pen Nanolithography,” NatureNanotechnology, 2007, Advanced On-line publication (11 pages).

Direct write methods, including DPN printing and pattern transfermethods, are described in for example Direct-Write Technologies,Sensors, Electronics, and Integrated Power Sources, Pique and Chrisey(Eds), 2002.

The direct-write nanolithography instruments and methods describedherein are of particular interest for use in preparing bioarrays,nanoarrays, and microarrays based on peptides, proteins, nucleic acids,DNA, RNA, viruses, biomolecules, and the like. See, for example, U.S.Pat. No. 6,787,313 for mass fabrication of chips and libraries; U.S.Pat. No. 5,443,791 for automated molecular biology laboratory withpipette tips; U.S. Pat. No. 5,981,733 for apparatus for the automatedsynthesis of molecular arrays in pharmaceutical applications.Combinatorial arrays can be prepared. See also, for example, U.S. Pat.Nos. 7,008,769; 6,573,369; and 6,998,228 to Henderson et al.

Scanning probe microscopy is reviewed in Bottomley, Anal. Chem., 1998,70, 425R-475R. Also, scanning probe microscopes are known in the artincluding probe exchange mechanisms as described in, for example, U.S.Pat. No. 5,705,814 (Digital Instruments).

Microfabrication methods are described in for example Madou,Fundamentals of Microfabrication, 2^(nd) Ed., 2002, and also Van Zant,Microchip Fabrication, 5^(th) Ed., 2004.

See for example U.S. Pat. No. 6,827,979 to Mirkin et al. is alsoincorporated by reference in its entirety.

US Patent Publication 2003/0022470 and Publication 2006/0228873 to Liuet al. describe cantilever fabrication methods.

US Patent Publication 2006/0040057 to King, Sheehan et al. describesthermal DPN printing methods.

Cantilevers

Some embodiments comprise devices comprising one or more cantilevers.Some cantilevers may be of microscopic dimension. Some cantilevers maybe of nanoscopic dimension. Some cantilevers may be used in such devicesas atomic microscopes, scanning microscopes, or nanoscopes. Somecantilevers may be used to deposit materials on surfaces, measure localheights of surfaces, perform local heating or cooling of surfaces, andthe like.

In some embodiments, cantilevers may comprise silicon nitride.Alternatively, they may comprise silicon carbide. These materials aretough polycrystalline ceramics, having high wear resistances. Bothsilicon nitride and silicon carbide are electrical insulators.Cantilevers made from these materials do not become electrically chargedas silicon cantilevers do. Control over electrostatic fields in thesecantilevers is improved over those made from silicon. Because thesematerials are also chemically inert, cantilevers made from them may alsobe used with biological materials. Silicon nitride may be more readilycommercially available than silicon carbide.

Some cantilevers may be configured into arrays. Such arrays may beone-dimensional. Some arrays may have more than one dimension. In someembodiments, cantilevers are configured into two-dimensional arrays.

Support Structures

Some cantilevers may be supported by a support structure or handlewafer. U.S. regular application Ser. No. 11/690,738 filed Mar. 23, 2007to Mirkin et al. describes support structures, which is herebyincorporated by reference in its entirety. Some support structures maybe non-transparent. They may be fabricated from substantiallynon-transparent materials or from transparent materials that arerendered substantially non-transparent. For example, the surface oftransparent borosilicate glass may be scratched, etched, roughened, orotherwise modified in such a way that it become substantiallynon-transparent.

Some support structures may be fabricated from single crystal silicon,which has several advantages over borosilicate glass. Hole etching maybe easier and less expensive. Difficulties bonding cantilevers tosupport structures caused by surface irregularities may also be avoided.Single crystal silicon may also provide for easier etching control.Alternatively, some support structures may be fabricated frompolycrystalline silicon.

Tips

Some cantilevers may comprise one or more tips. Some tips may comprisethe same materials as the rest of their cantilevers. In someembodiments, tips may comprise different materials than the rest oftheir cantilevers.

In some embodiments, tips may be able to be heated. Heating may beaccomplished by inductive heating, resonance heating, resistive heating,and the like. Where cantilevers comprise insulating materials, such assilicon nitride or silicon carbide, tips may be maintained attemperatures substantially higher than those of locations on thecantilever removed from such heated tips.

Some tips may extend below the rest of their cantilevers. Such tips maycontact a surface below their cantilevers. Some tips may take upsubstances from surfaces or deposit substances to surfaces. Some tipsmay heat surfaces or substances on surfaces. Some tips may be heated bysurfaces or substances on surfaces. Such tips are useful for use in suchapplications as thermal active pens.

Some tips may be scanning tips. Such tips may be used to detect featuresof surfaces or substances on surfaces below their cantilevers. Suchfeatures may include local physical dimensions such as height, localchemical compositions, and the like.

Some tips may be microscope tips, such as atomic microscope tips. Sometips may be nanoscope tips. Other variants will be understood by thoseskilled in the art.

Piezoresistors

Some cantilevers may comprise one or more piezoresistors. Piezoresistorsare resistors made from piezoelectric materials. The resistance of suchmaterials changes when subjected to mechanical stress. Examples ofpiezoelectric materials include, but are not limited to, germanium,polycrystalline silicon, amorphous silicon, silicon carbide, and singlecrystal silicon.

Piezoresistors may comprise heavily-doped silicon. The silicon can besingle crystal silicon or can be polycrystalline silicon. A preferreddopant is boron. A piezoresistor comprising silicon heavily-doped withboron can be substantially insensitive to changes in temperature. Such apiezoresistor may overcome the temperature compensation difficultiescommonly encountered by other designs that use lightly-doped silicon orintrinsic silicon, which are more sensitive to changes in temperature.Such a piezoresistor may also enable investigation of piezocapacitivestructures, which have not before been explored.

In some embodiments, such piezoresistors may be placed directly on thecantilever at locations where they can measure peak stress (related totip deflection) without themselves affecting substantially themechanical characteristics of the cantilever. This can improve fidelityof the measured stress relative to alternative designs.

In some embodiments, piezoresistors may comprise a Wheatstone bridgeconsisting of two active piezoresistors and two referencepiezoresistors. In preferred embodiments, the reference piezoresistorsare placed directly on the cantilever. In such a case, where thereference piezoresistors are placed in close proximity to the activepiezoresistors, electrical noise is diminished relative to bridges wherethe reference piezoresistors are remotely located. (Cf., e.g., such adesign in F. Goericke et al., Sensors and Actuators A143 (2008), pp.181-190, where remote piezoresistors were used without referencepiezoresistors.)

The number of piezoresistors on a cantilever need not be limited to one.For example, in one embodiment, multiple piezoresistors can be placed ona single cantilever. This design can allow two legs of a full Wheatstonebridge to be fabricated onto a single cantilever.

Sensing Height

Two fundamental activities associated with cantilevers are positioningtips over specific locations on a surface and determining the verticaldisplacements (heights) of the tips with respect to the surface. Bothactivities require knowledge of positions of the tips relative to theactuators that direct the cantilevers' movements. Such knowledge is notperfect, but is subject to several uncertainties.

One source of uncertainty is the fact that materials expand and contractin response to changes in temperature. Materials' responses arecharacterized by their coefficients of thermal expansion, which willdiffer according to composition. Where different materials are used, forexample in cantilevers and their tips, this uncertainty is compounded.Another source of uncertainty is the presence of built-in stresses thatmight be introduced during fabrication, which might lead to torsionalrotation in response to changes in temperature. Still another source ofuncertainty is actual physical bending or twisting of materials duringfabrication, introducing additional unforeseen positional offsets intothe devices.

Because of the small scales involved with cantilevers operating atmicroscopic or nanoscopic size scales, reducing such uncertaintiesduring design and fabrication important. Also helpful is having thecapability to detect changes in tip location in real-time duringcantilever operation. In some embodiments, one or more strain gaugesensors comprising piezoresistors may be fabricated on a cantilever, toenable real-time detection of variation in the position of one or moretips. Through use of multiple piezoresistors on a cantilever, theposition of maximum stress may be detected, which is related to tipdeflection.

An alternative strain gauge design comprises metal layers fabricated onthe cantilever. Such metals as chromium, nickel-chromium alloys,copper-nickel alloys, platinum, and platinum-tungsten alloys might beused. In some embodiments, the metal layers may comprise a serpentinestructure along the length of the cantilever. In some preferredembodiments, such serpentine structures are fabricated on two opposingsides of a cantilever. Such a configuration could double the sensitivityof the gauge and reduce electrical noise if configured into a halfWheatstone bridge. It also allows electrical cancellation of effectsthat would affect both structures, such as those introduced by thethermal coefficient of resistance of the strain gauge material or thepresence of local heat sources or sinks.

These piezoresistors and metal strain gauges may optionally be used inconjunction with other tip tracking methods, such as laser fluorometry.

Note that when tips are deflected due to contact with surfaces, theforce of contact may be estimated from the resistances measured from thepiezoresistors or strain gauges, owing to the relationship betweenstress and strain of the cantilever materials.

Fabricating Cantilever, Tips, Strain Gauges

In preparing the cantilever, one embodiment provides a cantilevercomprising a strain gauge structure comprising one or more tips, whereinthe cantilever is prepared by: (i) providing an oxidized silicon wafercomprising a silicon dioxide layer on silicon, (ii) patterning thesilicon dioxide layer to generate etch openings adapted for formation ofat least two tips, (iii) etching the silicon wafer anisotropically, (iv)depositing and patterning silicon nitride to form the cantilever, and(v) optionally bonding the cantilever to a handle wafer.

Fabrication of the pen can be carried out with the same basic processflow developed by Quate's group during the 1990's (1,2) and used byNanoInk to make various DPN pen systems.

In one embodiment, this process starts with a highly accurate e-beamwritten mask to pattern one or more square openings onto an oxidizedsilicon surface, which will become one or more tips. The openings can beof any size. For example, they can be between about 1 micron to about 60microns, such as between about 2 microns to about 50 microns. The sizeof the one or more openings can be the same or different from oneanother. Where more than one opening is used, v-trenches can bepatterned between multiple holes to form mechanical stiffeners in thenitride.

Subsequently, the wafer can be immersed in a KOH etch solution to etchanisotropically pyramidal pits into the silicon wafer to form the basictip mold(s) and the optional v-trenches. The masking oxide can then bestripped and the wafers re-oxidized at 950° C. for 360 minutes to growabout 3900 Å of silicon oxide. At this time and temperature, the oxideat the bottom of the pit is hindered with respect to growth, and thuswhen a cast film is deposited in this pit, the tip sharpness canapproach a 10 nm tip radius or smaller. No maximum limit of the tip sizeneed to be imposed. For instance, the tip size can be increased byincreasing the pit size.

Silicon nitride with low stress gradient can then be deposited onto themold wafer to form a cantilever. In one embodiment, the nitridethickness is about 600 nm. Accordingly, with this thickness and a widthof 25 um and a length of 200 um, a rectangular cantilever in thisembodiment can have a spring constant of about 0.04 N/m. While this is avalue that is commonly used for contact mode AFM probes and can workwell for DPN, other spring constants may also be obtained and used. Notto be bound by any particular theory, the spring constant changeslinearly with width w and with the third power of length L such that fora given thickness t, a wide range of spring constants K can be obtained:K=Ewt³/4L³, where E will depend on the materials of construction. In onealternative embodiment, the thickness of the nitride may also be changedon a batch basis to have a larger variation in spring constant. Forexample, nitride thicknesses from 400 nm to 1000 nm for cantilevers(with spring constant ranging from 0.0015 to over 1 N/m) have been usedby NanoInk for different applications.

The nitride can be oxidized, patterned, and etched to form thecantilevers and bonding area. In one embodiment, a borosilicate glasswafer can be further anodically bonded to the patterned nitride wafer.The borosilicate glass can be scribed with a dicing saw to form theindividual holder chips for each die before the tip mold wafer is etchedaway leaving the nitride cantilever attached to the borosilicate glasschip ready for use on the NanoInk's NSCRIPTOR™.

After the nitride is patterned, a photoresist layer is patterned forlift-off, and the strain-gauge metal is deposited and then lifted offthe nitride wafer. A second resist pattern is added where the nitridelayer will be bonded to the handle wafer. Subsequently, chromium,platinum, and gold is deposited and lifted off. A similar Cr/Pt/Au layercan be deposited on patterned handle wafer and then the two wafers arealigned and bonded using heat and temperature in a process such as goldthermocompression bonding. The wafers can then be etched intetramethylammonium hydroxide to remove the mold wafer and separate thehandle wafer into individual dice.

Fabricating Piezoresistors

Piezoresistors may be fabricated by a process comprising (i) forming atleast one piezoresistor in a handle wafer; (ii) forming at least onecantilever disposed on the handle wafer; (iii) annealing the handlewafer such that at least a portion of each piezoresistor is attached tothe cantilever; and (iv) selectively removing the handle wafer such thatat least the cantilever and the piezoresistors remain.

The silicon can be doped with a n-type dopant, such as boron. Theconcentration of the boron can be for example greater than 0.5×10²⁰atoms cm⁻³, such as at least 3×10²⁰ atoms cm⁻³. The dose of the dopantcan vary with the thickness. For instance, in one embodiment, whereinthe thickness is about 2 microns, the dose can be about 5×10¹⁶ atomscm⁻². The dopant can be introduced into the silicon by ion implantationor diffusion. In one embodiment, wherein ion implantation is employed,the ion implantation can be performed at 150 keV.

In some embodiments, some piezoresistors can serve to provide an etchstop for the subsequent KOH etch used to remove the undesired portionsof the silicon handle wafer. In other embodiments, the use of heavilyboron-doped silicon can help ensure the resistance of the structureremains substantially constant, even in the presence of a longer etchingtime, such as a doubling in etching time. The electrical and mechanicalproperties of such a structure can be highly resilient to processvariations.

In one embodiment, after the tip is sharpened, such as by the oxidationprocess discussed above, a wafer or layer of silicon nitride can bedeposited onto the tip and the handle wafer. In one embodiment, afterthe sharpening of the tip, about 0.1 microns to about 0.4 microns, suchas about 0.22 microns of the silicon handle wafer was consumed. Thesilicon nitride can later become the cantilever. Alternatively, siliconcarbide can be deposited. The handle wafer, with the newly formedcantilever and tip, can subsequently be annealed. Any suitable annealingconditions can be applied. In embodiment wherein the cantilevercomprises silicon nitride, the structure is annealed in an Argonatmosphere at about 1000° C.

During annealing, the dopant implanted into the handle wafer canmigrate. Annealing time will therefore generally affect the depth wiseconcentration of the dopant in the wafer. Although the dopant may not bein contact with the cantilever prior to annealing, the concentrationprofile can broaden during annealing to reach the interface between thewafer and the cantilever, finally being in contact with the cantilever.As shown in FIG. 1, the dopant concentration is confined to a certaindepth in the as-implanted sample, and it is not until after two or eventhree hours of annealing that the dopant profile broadens to a desirabledepth. In this embodiment, after three hours of annealing at about 1000°C. in Argon, a dopant implanted at 3×10²⁰ atoms cm⁻³ extends to depthsof about 0.22 μm to about 0.6 μm, averaging about 0.4 μm.

FIGS. 2A-2J illustrate various embodiments of the piezoresistor design.As it can been seen in the figures, the cantilevers can be in the formof an array. They can be used to detect force from various directions.For example, a “twist” sensor is referred to one sensor that can detecttorsional force. Similarly, the piezoresistor can be used to detectforce in the lateral or axial direction.

REFERENCES

-   (1) T. R. Albrecht, S. Akamine, T. E. Carver, and C. F. Quate,    “Microfabrication of cantilever styli for the atomic force    microscope,”J. Vac. Sci. Technol. A, Vac. Surf. Films (USA), 1990-   (2) S. Akamine, and C. F. Quate, “Low temperature oxidation    sharpening of microcast tips,” J. Vac. Sci. Technol B., vol. 10, No.    5, September/October 1992.

Non-Limiting Working Example Thermal Active Pen with PiezoresistorsFabrication Procedure

A Schematic flowchart of the procedure is provided in FIGS. 3A-3I.

-   1) Starting material (Nitride and Handle Wafers)-   2) Clean (Nitride Wafers)-   3) Oxidation (Nitride Wafers)-   4) Clean (Nitride Wafers)-   5) Tip lithography (Nitride Wafers)-   6) Descum-   7) Oxide Etch (Nitride Wafers)-   8) Strip Resist/Clean (Nitride Wafers)-   9) Piezoresistor implant lithography (Nitride Wafers)-   10) Piezoresistor implant (Nitride Wafers)-   11) Tip Etch (Nitride Wafers)-   12) Remove KOH Residue (Nitride Wafers)-   13) Strip Oxide (Nitride Wafers)-   14) Clean (Nitride Wafers)-   15) Oxidize (Nitride Wafers)-   16) Sharpen Lithography (Nitride Wafers)-   17) Inspect (Nitride Wafers)-   18) Oxide Etch (Nitride wafers)-   19) Strip Resist/Clean-   20) Deposit Silicon Nitride (Nitride Wafers)-   21) Piezoresistor Anneal/Drive-in (Nitride Wafers)-   22) Cantilever Lithography (Nitride Wafers)-   23) Frontside Nitride etch (Nitride Wafers)-   24) Backside Lithography (Nitride Wafers)-   25) Backside Nitride Etch (Nitride Wafers)-   26) Strip Resist/Clean-   27) Actuator Lithography (Nitride Wafers)-   28) Descum (Nitride Wafers)-   29) Deposit Metal (Nitride Wafers)-   30) Liftoff Metal (Nitride Wafers)-   31) Clean (Handle Wafers)-   32) Handle Recess Lithography (Handle Wafers)-   33) Silicon Etch (Handle Wafers)-   34) Strip Resist and Clean (Handle Wafers)-   35) Oxidize (Handle Wafers)-   36) Clean (Handle Wafers)-   37) TMAH Protect Lithography (Handle Wafers)-   38) Oxide Etch (Handle Wafers)-   39) Strip Resist and Clean (Handle Wafers)-   40) Handle Metal Lithography (Handle Wafers)-   41) Descum (Handle Wafers)-   42) Deposit Metal (Handle Wafers)-   43) Liftoff Metal (Handle Wafers)-   44) Clean (Nitride and Handle Wafers)-   45) Align and Bond Handle Wafer to Cantilever/Actuator Wafer    (Nitride and Handle Wafers)-   46) Silicon Etch (Bonded Wafer Assembly)-   47) Etch Back Oxide (Bonded Wafer Assembly)-   48) Remove Remnants of Corner Compensation Beams

1. A device comprising at least one cantilever comprising at least onepiezoresistor, wherein said at least one cantilever comprises siliconnitride or silicon carbide, wherein said at least one piezoresistor isdisposed on said at least one cantilever, and wherein said at least onepiezoresistor comprises silicon and at least one dopant, where said atleast one dopant is present at a concentration of at least 0.5×10²⁰atoms per cubic centimeter.
 2. The device according to claim 1, whereinsaid at least one cantilever comprises silicon nitride.
 3. The deviceaccording to claim 1, wherein said at least one dopant comprises ann-type dopant.
 4. The device according to claim 1, wherein said at leastone dopant comprises boron.
 5. The device according to claim 1, whereinsaid at least one piezoresistor comprises single crystal silicon.
 6. Thedevice according to claim 1, wherein said at least one piezoresistorcomprises polycrystalline silicon.
 7. The device according to claim 1,further comprising at least one strain gauge disposed on said at leastone cantilever.
 8. The device according to claim 1, wherein at least onecantilever comprises a first surface, a second surface, an at least onefirst strain gauge, and an at least one second strain gauge, whereinsaid first surface and said second surface are opposing, said at leastone first strain gauge is disposed on said first surface, and said atleast one second strain gauge is disposed on said second surface.
 9. Thedevice according to claim 1, wherein the at least one cantilevercomprise an array.
 10. The device according to claim 1, wherein the atleast one cantilever comprise an array, wherein said array isone-dimensional.
 11. The device according to claim 1, wherein the atleast one cantilever comprise an array, wherein said array istwo-dimensional.
 12. A thermally actuated probe comprising said at leastone cantilever according to claim
 1. 13. The device according to claim1, further comprising at least one tip.
 14. The device according toclaim 1, further comprising at least one microscope tip.
 16. The deviceaccording to claim 1, further comprising at least one atomic microscopetip.
 17. The device according to claim 1, further comprising at leastone scanning microscope tip.
 18. The device according to claim 1,further comprising at least one nanoscopic tip.
 19. The device accordingto claim 1, wherein said at least one cantilever comprises a tip and alocation displaced from said tip, wherein a first temperature of saidtip is substantially hotter than a second temperature of said locationdisplaced from said tip.
 20. The device according to claim 1, furthercomprising at least one metal contact, wherein said at least one metalcontact comprises one or more of Cr, Pt, Au.
 21. The device according toclaim 1, wherein said at least one cantilever has a length, a width, anda thickness, wherein the largest of said length, said width, and saidthickness is less than about 1000 μm.
 22. A method comprising: (i)forming at least one piezoresistor in a handle wafer; (ii) forming atleast one cantilever disposed on said handle wafer; (iii) annealing saidhandle wafer for a time, wherein said time is sufficient to allow saidat least one piezoresistor to contact said at least one cantilever; and(iv) separating at least a part of said hand wafer, so that said atleast one cantilever and said at least one piezoresistor remain incontact.
 23. The method of claim 22, further comprising forming at leastone tip disposed on said at least one cantilever.
 24. The method ofclaim 22, further comprising forming at least one metal contact on saidat least one cantilever, wherein said at least one metal contactcontacts said at least one piezoresistor.
 25. The method of claim 22,further comprising forming at least one metal contact on said at leastone cantilever, wherein said at least one metal contact contacts said atleast one piezoresistor, further wherein said at least one metal contactcomprises one or more of chromium, platinum, or gold.
 26. The method ofclaim 22, wherein said forming at least one piezoresistor comprises ionimplantation or ion diffusion.
 27. The method of claim 22, wherein saidhandle wafer comprises single crystal silicon.
 28. The method of claim22, wherein said handle wafer comprises polycrystalline silicon.
 29. Themethod of claim 22, wherein said at least one piezoresistor comprisessingle crystal silicon.
 30. The method of claim 22, wherein said atleast one piezoresistor comprises polycrystalline silicon.
 31. Themethod of claim 22, wherein said at least one piezoresistor comprisesboron.
 32. The method of claim 22, wherein said at least onepiezoresistor comprises at least about 0.5×1020 atoms/cm³ of boron. 33.The method of claim 22, wherein said cantilever comprises siliconnitride.
 34. The method of claim 22, wherein said cantilever comprisessilicon carbide.
 35. The method of claim 22, wherein said annealing saidhandle wafer is performed in an Argon atmosphere at about 1000° C. 36.The method of claim 22, wherein said annealing said handle wafer isperformed for about 3 hours.
 37. The method of claim 22, wherein said atleast one piezoresistor after said annealing said handle wafer has athickness of between about 0.1 μm to about 0.8 μm.
 38. The method ofclaim 22, wherein the at least one piezoresistor after said annealingsaid handle wafer has a thickness of about 0.4 μm.
 39. The method ofclaim 22, further comprising forming at least one oxide layer disposedon said handle wafer.
 40. The method of claim 22, further comprisingforming at least one oxide layer disposed on said handle wafer, whereinsaid handle wafer comprises polycrystalline silicon doped with an n-typedopant.
 41. The method of claim 22, further comprising forming at leastone oxide layer disposed on said handle wafer, wherein said handle wafercomprises polycrystalline silicon doped with boron.
 42. A methodcomprising: measuring at least one resistance of at least onepiezoresistor, determining a maximum or minimum resistance of said atleast one resistance, determine a specific location corresponding tosaid maximum or minimum resistance, calculating a tip deflection,wherein said at least one piezoresistor are disposed on at least onecantilever, said at least one cantilever having a length, a width, and athickness, and wherein the largest of said length, said width, and saidthickness is less than about 1000 μm.
 43. The method according to claim42, wherein said at least one piezoresistor are part of the device ofclaim
 1. 44. The method according to claim 42, wherein said at least onepiezoresistor comprises silicon and at least one dopant.
 45. The methodaccording to claim 42, wherein said at least one piezoresistor comprisessilicon and boron.
 46. The method according to claim 42, wherein saidtip deflection is calculated using said specific location.
 47. Themethod according to claim 42, wherein said tip deflection is calculatedusing said maximum or minimum resistance.
 48. The method according toclaim 42, wherein said tip deflection is calculated using said at leastone resistance.
 49. The method according to claim 42, further comprisingcalculating a force.
 50. A method comprising: measuring at least oneresistance of at least one strain gauge, determining a maximum orminimum resistance of said at least one resistance, determine a specificlocation corresponding to said maximum or minimum resistance,calculating a tip deflection. wherein said at least one strain gauge aredisposed on at least one cantilever, said at least one cantilever havinga length, a width, and a thickness, and wherein the largest of saidlength, said width, and said thickness is less than about 1000 μm. 51.The method according to claim 50, wherein said at least one strain gaugeare part of the device of claim
 1. 52. The method according to claim 50,wherein said at least one strain gauge comprises one or more ofchromium, nickel-chromium alloy, copper-nickel alloy, platinum, orplatinum-tungsten alloy.
 53. The method according to claim 50, whereinsaid tip deflection is calculated using said specific location.
 54. Themethod according to claim 50, wherein said tip deflection is calculatedusing said maximum or minimum resistance.
 55. The method according toclaim 50, wherein said tip deflection is calculated using said at leastone resistance.
 56. The method according to claim 50, further comprisingcalculating a force.